This invention relates to a water jet propulsion boat and more particularly to an improved jet propulsion unit for a watercraft and method of mounting the jet propulsion unit.
The advantages of employing water jet propulsion units for watercraft are well known. Among these advantages, is the ability to operate the watercraft in very shallow water and at high speeds. In addition, if the jet propulsion unit is mounted in a tunnel on the underside of the hull of the watercraft it also affords a very neat and compact arrangement for the watercraft as well as a good appearance. However, when so mounted there are certain difficulties that arise.
Specifically, the propulsion unit normally has a downwardly facing water inlet portion through which water is drawn by the impeller of the jet propulsion unit for discharge through a rearwardly facing discharge nozzle. Unlike outboard motors or the outboard drive of an inboard/outboard drive, however, it is not possible, with prior art type of constructions to move the jet propulsion unit up out of the water when the watercraft is not operating. As a result, the water inlet is normally submerged at all times and hence may be subject to the formation of barnacles and other incrustation. In addition, because of its ability to operate in shallow water, frequently the jet propulsion unit water inlet can clog with seaweed or other foreign materials.
To obviate these disadvantages, it has been proposed to mount the jet propulsion unit so that it can rotate about a longitudinally extending axis so as to bring the water inlet portion up out of the water when not in use. In addition, by providing an access opening in the hull, it will be possible to clean foreign materials from the water inlet when the jet propulsion unit is rotated to its out of the water position.
Although the aforedescribed construction has numerous advantages, as aforenoted, it also has some difficulties. Normally, the jet propulsion unit and the watercraft powered by it are steered by a pivotally supported steering nozzle disposed in proximity to the jet propulsion unit discharge nozzle. This steering nozzle is remotely operated. However, when the jet propulsion unit is rotatable about a longitudinally extending axis, then the interconnection with a remote steering control can present obvious difficulties.
Furthermore, it is frequently the practice to provide a reverse thrust bucket for cooperating with the discharge of the jet propulsion units so as to permit reverse propulsion. Again, the remote operation of said reverse thrust buckets can present substantial problems if the jet propulsion unit is rotatable about a longitudinally extending axis.
It is, therefore, a principal object to this invention to provide an improved water jet propelled boat in which the water jet propulsion unit has its water inlet rotatable about a longitudinally extending axis for cleaning, servicing and to bring it out of the water without necessitating rotation of the discharge nozzle, steering nozzle and reverse thrust bucket.
It is a further object to this invention to provide an improved mounting arrangement for a water jet propulsion unit wherein only a portion of the water jet propulsion unit is rotatable for servicing.
In addition to or in lieu, of having the water jet propulsion unit rotatable about a longitudinally extending axis for the aforenoted purposes, it has also been proposed to permit pivotal movement of the water jet propulsion unit about a transversely extending axis for the same purposes. If the unit is only pivotal about the transverse axis, this minimizes some of the aforenoted difficulties in connection with controlling the steering and reverse thrust bucket. However, another problem arises in connection with such constructions.
Previous water jet propulsion units that are pivotal about transverse axes, have employed a pair of arcuate arms on opposite sides of the jet propulsion unit that are slotted and receive pins carried by the jet propulsion unit so as to control its pivotal movement. The arms also serve the purpose of taking the transverse thrust. It is important that the transverse thrust be adequately absorbed due to the fact that the jet propulsion unit is steered in the aforenoted described manner. However, when pin and slot arrangements are employed, clearance is a necessity and this can give rise to problems.
It is, therefore, a still further object to this invention to provide an improved arrangement for pivotally supporting a jet propulsion unit for movement about a transverse axis while absorbing all side thrusts without the necessity of incorporating clearances.